The present invention relates to handles for manually operated endodontic instruments.
Endodontic instruments are those which are used to perform the various phases of endodontic, or root canal, treatment. The first steps in a root canal treatment involve opening the canal, followed by a reaming, or filing, operation to increase the canal diameter.
While power driven instruments have been developed, and are used, for these operations, there remains a place in the field for manually operated instruments.
The successful use of endodontic instruments, and particularly manually operated instruments, depends to a substantial degree on the skill of the practitioner and his ability to precisely control the movements of the instrument. In this connection, the handle of the instrument is of considerable importance because of its influence on the precision with which the practitioner can control the movements of the element acting in the root canal, which element is generally a very thin file. Such file most commonly has a helical structure. For example, a Kerr file is constituted by a steel wire which is tapered toward its free end and is twisted about its axis to form a helical structure. The initial cross section of the wire is generally triangular or square. Other file types, such as the Hedstrem file, are also known.
The canal in a tooth is initially a very small diameter and often follows a curved path. In order to open such a canal by means of a file, the practitioner must apply to the file a movement which combines pushing and rotational components to permit the file to penetrate into, and advance along, the path of the canal.
In order to subsequently enlarge the canal, its walls must be reamed or filed. The movements required vary from one file type to another. Thus, in the case of a Hedstrem file, movements including rotation and pulling components must be imposed in order to cause the file blades to cut into the tooth dentine, and a pulling force must be applied to extract the cuttings, or filings. In the case of a Kerr file, a longitudinal back and forth filing movement is appropriate to cause the teeth or blades of the file to rub against the canal walls.
The effectiveness of such instruments is dependent to a substantial extent on their handle, because the shape of the handle determines the ease with which the practitioner can produce, and control, the various types of movements, dictated by the conditions encountered within the canal. Thus, the handle, which is normally grasped between the thumb and index finger, must be gripped so that, in certain circumstances, rotation of the file is prevented, and, in other circumstances, a controlled rotation is imparted thereto.